1. Böhlke, J. K. and J. M. Denver (1995): Combined use of groundwater dating, chemical, and isotopic ana lyses to resolve the history and fate of nitrate contamination in two agricultural watersheds, Atlantic coastal plain, Maryland. Water Resources Research, 31(9). 2319-2339.
2. Böhlk e, J. K., R. Wanty, R., Tuttle, M., Delin, G. and M. London (2002): Denitrification in recharge area and discharge area of a transient agricultural nit r ate plume in a glacial outwash sand aquifer, Minn esota. Water Resources Research, 38(7). 10-1-10-26.
3. Gallardo, A. H., Borja, VAR. and N. Tase (2005): Flow and patterns of nitrate pollution in groundwate r: a case study an agricultural area in Tsukuba City, Ja pan. Environmental Geology, 48(7). 908-919.
4. Korom, S. F. (1992): Natural Denitrification in the Saturated Zone: A Review. Water Resources Researc h, 28(6). 1657-1668.
5. Okada, R., Tase, N., Tamura, K., Negishi, M., and Takagi, K. (1999): Fate of fertilizer from surface to groundwater -How much does it accumulate in the soil?-. Proceedings of the International Symposium on Groundwater in Environmental Proble ms, Chiba University, 57-62.